1. Field of the Invention
The present invention relates to an optical apparatus such as an imaging apparatus having a focus adjustment function and a method for controlling the same.
2. Description of the Related Art
Conventionally, in electronic still cameras or video cameras or the like, an autofocus (below, abbreviated “AF”) is used. In AF control, the controller of the camera calculates the focal position of the focus lens based on image data that is read out from an imaging element that uses a CCD (charge coupled device) and the like or data that has been read out from a dedicated distancing sensor. The controller moves the focus lens to the focal position by controlling a motor, and carries out the imaging operation after the movement has ended. In this context, because the focus lens oscillates in the optical axis direction due to inertia immediately after the focus lens has been stopped, there is a concern that this may influence the image quality if a photograph is taken immediately. Thus, the controller starts imaging after waiting for a specific time to pass until the oscillation of the focus lens converges.
Various technologies have been proposed to handle the influence that the oscillation and misalignment of the focus lens in the optical axis direction has on a image. In the apparatus disclosed in Japanese Patent Laid-open No. H07-115580, the blur amount at the focal plane is calculated based on the value of the diaphragm. This is the blur amount at the focal plane in relation to a unit drive amount of a pulse motor that drives the focus lens. This apparatus changes the pulse number of a pulse motor in correspondence to the amount that the focus lens has overshot the focal peak point based on the calculated value of the blur amount.
Here, originally the oscillation of the focus lens in the optical axis direction may converge within a range that does not influence the image quality, and the convergence range at this time differs depending on the imaging conditions. However, in a conventional apparatus, irrespective of the imaging conditions, the apparatus simply waits until the oscillation is within a fixed convergence range. Thus, needless waiting time occurs, and there is a concern that this will hinder speedy photography.